Active thermal management method for motor drive of an aircraft

Abstract

The application discloses an active thermal management method for a motor driver of an aircraft. The method adopts temperature-sensitive electrical parameters to construct a thermal network and comprehensively considers measured temperature of a temperature sensor, and performs active thermal management control from three aspects of driving parameter, modulation strategy and working cycle to inhibit overall temperature fluctuation of the driver, balance temperature of the same bridge arm and balance temperature of the same phase and different bridge arms. The application has the beneficial effects that: the working state of the driving device is actively and overall adjusted, the temperature of the aircraft driving unit is balanced and stabilized, and the operation and maintenance cost of the driver is reduced; the real-time and accuracy of temperature collection are considered, the method has strong practicability and wide application prospect; and the method has unique advantages in the fields of inhibiting temperature fluctuation of the power device and prolonging the service life of the driver.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and in particular to an active thermal management method for an aircraft motor drive. Background Technology

[0002] The rotor motor's drive is a crucial component of an aircraft, responsible for energy conversion and motion control. Its stable operation is vital to the aircraft's reliability and safety. Excessive drive operating temperature can lead to motor malfunction or shutdown, causing aircraft instability or even a crash, resulting in irreversible damage. Furthermore, power devices, as the most critical semiconductor components in the drive, are directly related to the stability and lifespan of the entire drive system. Improving the utilization rate of power devices and extending their service life not only enhances the economic efficiency of aircraft operation but also reduces the risk of structural reliability degradation due to frequent component replacements. Therefore, timely monitoring and management of the motor drive's power devices are of paramount importance.

[0003] Power devices act as switches connecting low-voltage and high-voltage circuits in equipment. Most of the heat generated by drivers originates from these power devices, and heat-related driver damage accounts for 55% of all device failures. This underscores the importance of driver thermal management. Thermal management is primarily divided into internal and external approaches. Effective external thermal management utilizes heat dissipation technology to reduce temperature without affecting driver operation. Techniques such as customized heat sink fin designs, high-efficiency liquid cooling, oil spray cooling, and optimized metal heat sinks provide simple and flexible thermal management measures for drivers, reducing device operating temperatures, extending device lifespan, and improving equipment stability. However, these methods also have limitations. For example, while liquid cooling can rapidly reduce device temperature, it requires an additional control system; oil cooling requires less additional space, but places high demands on the overall oil circuit design of the motor and controller, making it challenging; phase change material coupling heat dissipation can optimize heat dissipation capacity, but requires significant space and reduces system power density. These methods are not suitable for equipment like aircraft, which have high requirements for motor thrust density.

[0004] In recent years, the rapid development of microprocessor devices, sensor acquisition instruments, and information processing technologies has provided reliable hardware and technical conditions for more real-time and intelligent internal thermal management. Internal thermal management is divided into device-level and system-level approaches. Device-level management primarily optimizes temperature by adjusting device operating conditions, such as adjusting switching frequency, changing duty cycle, adding buffer circuits, and changing drive resistance and drive voltage. System-level management mainly controls electrical parameters, such as adjusting bus voltage and current, rationally allocating active and reactive power, optimizing modulation strategies, and dynamically adjusting parallel devices. Among these, changing the switching frequency and bus current is effective, simple to operate, and low-cost in both device-level and system-level thermal management, making it suitable for aircraft actuators. However, changes in switching frequency affect the actuator output waveform, and adjusting the bus current requires comprehensive consideration of the system's operating state. How to achieve thermal management while comprehensively minimizing these impacts is a hot research topic for the future.

[0005] Based on their motion characteristics and technical requirements, aircraft actuators draw a large current during startup. Currently, redundant designs are commonly used, where multiple power devices are connected in parallel to meet startup requirements, and the current is distributed among the parallel devices during normal operation. However, due to differences in manufacturing processes, inherent characteristics, and usage, individual power devices vary significantly in terms of lifespan and operating temperature. Without active thermal management, devices with higher operating temperatures will further increase their operating temperature, reducing the overall actuator lifespan. Therefore, balancing and fully utilizing power devices to improve actuator lifespan has become an urgent problem to be solved.

[0006] Current external thermal management methods typically require additional control circuitry or larger heat dissipation areas. However, the weight of aircraft needs to be strictly controlled to improve its operating power density, making it impossible to achieve a balance between stability and efficiency. While various methods can control temperature for internal thermal management, their control effects differ, and their application timescales vary, lacking comprehensive consideration. Furthermore, actuators are widely used and face diverse operating conditions, requiring more specific active thermal management methods to reduce their impact on equipment operation. However, there is a lack of specific active thermal management strategies for aircraft actuators. Due to individual differences in power devices, the prediction, planning, and full utilization of the lifespan of multiple parallel power devices in aircraft are not yet comprehensive enough. Further research and exploration are needed for integrated online and offline active thermal management of aircraft actuators. Summary of the Invention

[0007] The present invention aims to overcome the aforementioned deficiencies in the prior art and provides an active thermal management method for an aircraft motor driver that enables temperature uniformity and stability of the aircraft drive unit and improves its service life.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: An active thermal management method for an aircraft motor driver is proposed. This method utilizes a thermal network constructed with temperature-sensitive electrical parameters and a temperature sensor to comprehensively measure temperature. Active thermal management control is implemented from three aspects: suppressing overall temperature fluctuations of the driver, equalizing the temperature of the same bridge arm, and equalizing the temperature of different bridge arms in the same phase, based on drive parameters, modulation strategies, and duty cycles. The specific active thermal management control method is as follows: (1) Overall temperature fluctuation suppression management: The aircraft will experience temperature fluctuations due to changes in heat dissipation conditions and load. The switching loss and conduction loss are considered in combination for coordinated control. The current amplitude is dynamically limited and the switching frequency is adjusted. At the same time, the temperature change rate is monitored and the current change rate is limited to slow down the temperature change. (2) Temperature equalization management of the same bridge arm: The temperature difference of the upper and lower power devices of the three-phase bridge arm is classified and the DPWM or SVPWM modulation algorithm with "111" as the zero vector or "000" as the zero vector is selected according to the result. While ensuring the output waveform quality, the overall condition of the three-phase bridge arm is taken into account to balance the temperature and extend the overall service life of the driver. (3) Temperature balance management of different bridge arms in the same phase: When the temperature of the bridge arms in the same phase of different drive modules is not uniform, the working state of the device in each electrical cycle is changed according to the temperature difference, and the equivalent current value flowing through the bridge arm is adjusted to balance the temperature of the same phase.

[0009] This invention proposes an active thermal management method for aircraft motor drivers. This method proactively and comprehensively adjusts the operating state of the drive components, resulting in a more balanced and stable temperature within the aircraft drive unit, thus reducing driver maintenance costs. The proposed active thermal management method for aircraft motor drivers balances the real-time nature and accuracy of temperature acquisition, providing comprehensive active thermal management of the driver. It is highly practical and has broad application prospects. Therefore, this active thermal management method for aircraft motor drivers has unique advantages in suppressing temperature fluctuations in power devices and extending the lifespan of the driver.

[0010] Preferably, the active thermal management process for the aircraft motor driver is as follows: (a) During the self-test of the aircraft, the upper and lower power devices of different bridge arms are turned on and 1.5 times the rated current is injected for a short time. The on-state voltage drop of the device is obtained through the voltage acquisition circuit. Based on the principle that the on-state voltage drop is positively correlated with the degree of aging, the parameters of the thermal network are corrected and updated. (b) When the aircraft starts up, the motor speed is required to increase rapidly and the current carrying capacity is large. Therefore, all bridge arms are in full operation and no temperature control is performed on them. (c) After the aircraft is running stably, the torque and speed of the motor and the temperature of the controller also tend to stabilize. At this time, the driver is subjected to comprehensive active thermal management, including suppression of overall driver temperature fluctuations, equalization of temperature of the same bridge arm, and equalization of temperature of different bridge arms in the same phase. (d) When the aircraft lands, the current is gradually reduced. Temperature control is not required at this time, but the average temperature of the power devices collected by the NTC temperature sensor during the aircraft operation can be stored for updating the thermal network parameters.

[0011] As a preferred embodiment, in method (1), specifically: when the aircraft increases its rotational speed due to attitude adjustment or the heat dissipation conditions deteriorate, the overall temperature of the driver will rise in stages. At this time, the switching frequency is appropriately reduced to reduce the switching loss of the power device, and the current amplitude is limited to limit the conduction loss of the power device. At the same time, the temperature change rate is monitored, and the current change rate is limited by the model prediction method, thereby reducing the driver temperature rise. Similarly, when the overall temperature of the driver drops in stages, the switching frequency and current limit are appropriately increased, and the negative change rate of the current is limited to reduce the driver temperature drop.

[0012] Preferably, when the overall temperature rise of the driver exceeds the maximum threshold, the switching frequency is reduced to reduce the switching loss of the power device, and the maximum current and rate of change are limited to reduce the conduction loss of the power device; when the overall temperature drop of the driver is below the minimum threshold, the switching frequency is increased to increase the switching loss of the power device, and the minimum current and rate of change are limited to increase the conduction loss of the power device.

[0013] As a preferred method, in method (2), the number and status of the bridge arms with excessive temperature difference between the upper and lower power devices of the three-phase bridge arm are discussed and classified. The temperature difference between the upper and lower power devices of the bridge arm is evaluated based on the classification results. When the operating temperatures of the upper and lower power devices are not significantly different, SVPWM with better modulation performance is adopted. If the temperature of the upper tube of a typical bridge arm is greater than that of the lower tube and exceeds the threshold, DPWM with "000" as the zero vector switching is adopted. Otherwise, DPWM with "111" as the zero vector switching is adopted. By managing the conduction loss when the zero vector is applied, the loss of the higher temperature power device is weakened and the loss of the lower temperature power device is compensated, so that the temperature difference is reduced and the aging process of the devices in the same bridge arm is balanced.

[0014] As a preferred method, in method (3), the driver adopts a redundant design to meet the starting current requirements of the aircraft. During normal operation, the current is shunted by the bridge arms of the same phase. If the temperature of one bridge arm is greater than the temperature of the other bridge arms and exceeds the threshold, the working state of its electrical cycle is adjusted according to the difference. During the operation of the aircraft, this can be equivalent to the reduction of the effective current flowing through the overheated bridge arm, the reduction of conduction loss, thereby reducing the temperature and balancing the service life of the power devices.

[0015] Preferably, the driver includes a printed circuit board, a power device, an NTC temperature sensor, a conductor copper pillar, a heat sink, a relay, and a bus capacitor. The printed circuit board has a microcontroller control circuit, a signal acquisition and processing circuit, a motor drive circuit, and a power supply circuit. There are two printed circuit boards placed opposite each other. The power device is placed on the upper and lower sides of the printed circuit board. The bus capacitor and the relay are placed between the two printed circuit boards and arranged around the printed circuit board. The two printed circuit boards are supported by conductor copper pillars and electrically connected to the circuits on the upper and lower printed circuit boards. The NTC temperature sensor is placed close to the power device and between the power device and the printed circuit board. The heat sink is located at the upper and lower ends of the printed circuit board and is close to the power device.

[0016] Preferably, the driver, except for the heat sink, is encapsulated in a stainless steel metal shell. Waterproof aviation plugs are used when the relay and bus capacitor are connected to the external circuit. The stainless steel metal shell of the driver is connected to the shielding layer of the signal cable.

[0017] The beneficial effects of this invention are: it proactively coordinates and adjusts the working state of the drive components, making the temperature of the aircraft drive unit more balanced and stable, thus reducing the operation and maintenance costs of the drive; it takes into account both the real-time performance and accuracy of temperature acquisition, making it highly practical and with broad application prospects; and it has unique advantages in suppressing temperature fluctuations of power devices and extending the service life of the drive. Attached Figure Description

[0018] Figure 1 This is a flowchart of an active thermal management system for an aircraft motor driver proposed in this invention. Figure 2 This is a diagram of an active temperature fluctuation suppression control strategy for an aircraft motor driver proposed in this invention. Figure 3 This is a diagram illustrating the thermoelectric bridge arm number and state classification strategy for an aircraft motor driver proposed in this invention. Figure 4 This is a diagram of an active equalization and bridge arm temperature modulation strategy for an aircraft motor driver proposed in this invention. Figure 5 This is a diagram of an active in-phase temperature equalization strategy for different bridge arms of an aircraft motor driver proposed in this invention. Figure 6 This is a three-dimensional structural diagram of an implementation platform for an active thermal management system for an aircraft motor driver proposed in this invention. Figure 7 This is an exploded schematic diagram of a platform component for implementing active thermal management of an aircraft motor driver proposed in this invention. Figure 8This is an equivalent circuit diagram of an implementation platform for an active thermal management system for an aircraft motor driver proposed in this invention.

[0019] Figure 6 , Figure 7 In the diagram: 1 is the printed circuit board, 2 is the power device, 3 is the NTC temperature sensor, 4 is the conductor copper pillar, 5 is the heat sink, 6 is the relay, and 7 is the bus capacitor. Detailed Implementation

[0020] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0021] The active thermal management process for the aircraft motor drive proposed in this design is as follows: Figure 1 As shown, during the aircraft's self-test, the upper and lower power devices of different bridge arms are turned on, and 1.5 times the rated current is injected briefly. The on-state voltage drop of the devices is obtained through the voltage acquisition circuit. Based on the principle that the on-state voltage drop is positively correlated with the degree of aging, the parameters of the thermal network are corrected and updated. Since the voltage acquisition points of the same phase of the complete set of bridge arms are exactly the same, the measurement circuit can be shared. That is, the number of voltage acquisition circuits does not increase with the number of three-phase bridge arms, but always remains at six. During measurement, the power devices of non-target bridge arms are kept off. When the aircraft starts up, the motor speed is required to increase rapidly and the current carrying capacity is large. Therefore, all bridge arms operate at full capacity without temperature control. The advantage of this is that the performance of the driver can be fully utilized to meet short-term requirements. The inertia of temperature change is large. During startup, the difference between the ambient temperature and the operating temperature of the driver is large, resulting in a long temperature rise time. This provides an over-temperature margin for high-current startup, so no control is required. After the aircraft stabilizes, the motor torque and speed, as well as the controller temperature, also tend to stabilize. At this time, comprehensive active thermal management is performed on the driver to suppress overall driver temperature fluctuations, balance the temperature of the same bridge arm, and balance the temperature of different bridge arms in the same phase.

[0022] When an aircraft increases its rotational speed due to attitude adjustments or when heat dissipation conditions worsen, the overall actuator temperature will rise in stages. In this case, appropriately reducing the switching frequency reduces the switching losses of power devices, limiting the current amplitude limits the conduction losses of power devices, and simultaneously monitoring the rate of temperature change and using model prediction to limit the rate of current change, thereby reducing the magnitude of the actuator temperature rise. Similarly, when the actuator cools down in stages, appropriately increasing the switching frequency and current limit, and limiting the negative rate of current change, reduces the magnitude of the actuator temperature drop. Throughout this process, PI control is introduced to ensure rapid and stable adjustment.

[0023] The choice of modulation significantly impacts the driver's temperature distribution. Therefore, it's necessary to discuss the number of bridge arms with excessive temperature differences between the upper and lower components to ensure the selected modulation method addresses both the problem of excessive temperature differences between the upper and lower components in a typical bridge arm and the overall performance. Next, the temperature difference between the upper and lower components in a bridge arm is evaluated based on the classification results. When the operating temperatures of the two components are similar, SVPWM with better modulation performance is used. If the temperature of the upper component in a typical bridge arm is higher than that of the lower component and exceeds a threshold, DPWM with "000" as the zero-vector switching is used; otherwise, DPWM with "111" as the zero-vector switching is used. By managing the conduction losses during zero-vector operation, losses are reduced for higher-temperature components and compensated for for lower-temperature components, thus reducing the temperature difference and balancing the aging process of components within the same bridge arm.

[0024] To meet the starting current requirements of the aircraft, the driver adopts a redundant design, with current shunted by the same-phase bridge arms during normal operation. If the temperature of one bridge arm is higher than that of the other bridge arms and exceeds a threshold, the operating state of its electrical cycle is adjusted according to the difference. During aircraft operation, this can be equivalent to a reduction in the effective current flowing through the overheated bridge arm, a reduction in conduction losses, thereby lowering the temperature and balancing the lifespan of the power devices.

[0025] During aircraft landing, the current is gradually reduced. Temperature control is not required at this time, but the average temperature of the power devices collected by the NTC sensor during aircraft operation can be stored for updating thermal network parameters.

[0026] For the three methods of integrated active thermal management, we will provide specific implementation methods and hardware platforms for one working scenario.

[0027] The main components of the implementation platform are as follows Figure 6 , Figure 7 As shown, 1 is a printed circuit board, 2 is a power device, 3 is an NTC temperature sensor, 4 is a conductor copper pillar, 5 is a heat sink, 6 is a relay, and 7 is a bus capacitor. Printed circuit board 1 is located in the center of the driver and contains a microcontroller control circuit, signal acquisition and processing circuit, motor drive circuit, and power supply circuit. Power device 2, bus capacitor 7, and relay 6 occupy a relatively large space, therefore... Figure 6 , Figure 7 The detailed layout is as follows: two printed circuit boards 1 are placed opposite each other; power devices 2 are placed on the upper and lower sides, with the left side consisting of the upper bridge arm and the right side consisting of the lower bridge arm. Identical phase bridge arms are arranged according to... Figure 8 The staggered arrangement shown is as shown on the upper plate. Bridge arm and lower plate Bridge arm alignment, upper plate Bridge arm and lower plate The bridge arms are aligned, which prevents one phase from overheating and improves thermal management. Bus capacitors 7 and relays 6 are arranged around the perimeter of printed circuit board 1, placing low-voltage circuits such as control circuits in a more central location, facilitating wiring design. The main circuit of printed circuit board 1 uses a large copper area to increase current carrying capacity and optimize heat dissipation; other circuits are arranged in multiple layers to improve space utilization. Conductive copper pillars 4 are used for support between the two printed circuit boards, while also connecting the main circuits of the upper and lower boards. The NTC temperature sensor 3 is placed close to the power device; its resistance is negatively correlated with temperature. Temperature signal processing requires converting the housing temperature measured by the NTC temperature sensor 3 into the device junction temperature using a thermal network. Heat sinks 5 are located on the upper and lower parts of the driver, increasing the contact area with the outside and reducing heat accumulation during power device operation.

[0028] Due to the complex and variable operating environment of the driver, the circuit components, except for heatsink 5, can be encapsulated in a stainless steel metal casing to ensure heat dissipation and prevent external environmental factors from causing driver failure. Waterproof aviation connectors are used when connecting relay 6 and bus capacitor 7 to the external circuit. The driver's metal casing should be connected to the shielding layer of the signal cable to ensure good grounding at one end and reduce external electromagnetic interference to the driver. Where space permits, bridge arms can be flexibly added according to the motor starting current requirements and the parameter values ​​of the power devices.

[0029] The expressions for the switching loss and conduction loss of power devices are as follows: in, For switching frequency, and These represent the power consumption when the power device is turned on and off, respectively. For the current flowing through the power device, This is the DC bus voltage. For motor power factor, The modulation ratio, This is the on-resistance of the power device.

[0030] Without considering modulation ratio and power factor, and removing relatively constant quantities such as bus voltage, on-state voltage drop, and device switching power consumption, it is evident that power device losses are highly correlated with frequency and current. Therefore, the temperature of power devices is related to frequency and current, as expressed below: in, This refers to the junction temperature of the power device, i.e., the actual operating temperature of the semiconductor.

[0031] like Figure 2 As shown, The overall positive temperature uncontrolled threshold, The overall negative temperature uncontrolled threshold, The maximum threshold for overall positive temperature. This represents the maximum threshold for overall negative temperature. When the aircraft is operating normally, the temperature is at... and The temperature fluctuates within a certain range without temperature control. When a sudden load increase or poor heat dissipation occurs, the overall driver temperature rises accordingly: exceeding... At this time, the current amplitude is limited, and the limit value is appropriately increased as the temperature rises. This limits conduction losses to restrict temperature rise while also taking into account the rapid changes in motor speed and torque. The switching frequency is linearly reduced as the temperature rises to reduce switching losses and thus reduce the rise in driver temperature. At this time, the current amplitude is strictly limited to prevent irreversible damage to the driver from overcurrent, the switching frequency is reduced to the minimum allowable value of the system, and the high temperature suppression is strengthened. When a sudden load reduction or good heat dissipation occurs, the overall temperature of the driver decreases. To reduce the shortening of driver life due to temperature fluctuations, losses are appropriately increased to maintain temperature balance: the frequency and current amplitude control process is basically similar to the temperature rise process, below which... At this time, the dynamic limit current amplitude decreases, the switching frequency is dynamically increased, and the overall temperature drop of the driver is slowed down; below At that time, the current amplitude is kept constant, the maximum switching frequency is used, and the temperature compensation is increased.

[0032] In addition to suppressing temperature fluctuations, temperature differences are monitored and the rate of change of current is controlled to improve the speed of thermal management, such as... Figure 2 As shown, The overall positive temperature uncontrolled rate of change, The overall rate of change under negative temperature is uncontrolled. This represents the maximum rate of change at the overall positive temperature. This represents the maximum rate of change in overall negative temperature. Maximum current change rate limit, To limit the rate of change of current, the thermal management process is as follows: exceeding At that time, adopt a larger Limit the power output of the motor while suppressing temperature rise; exceed At that time, Stricter restrictions, increased efforts to suppress temperature rise; below At that time, use a smaller Limit; below At that time, The restrictions are more stringent, and the temperature compensation is increased.

[0033] Due to differences in manufacturing processes, inherent characteristics, and usage, power devices can have different operating temperatures on the same bridge arm or different bridge arms in the same phase, which in turn leads to different lifespans for each device and shortens the service life of the driver. Figure 3 This is a detailed flowchart illustrating the active bridge arm temperature control strategy in an embodiment. For the junction temperature difference of the upper and lower components of the same bridge arm; The discussion proceeds as follows: When there is no excessive temperature difference in any bridge arm, the equalization bridge arm temperature control is directly implemented, and SVPWM modulation is selected. When there is an excessive temperature difference, the number of bridge arms exceeding the limit is determined: Taking one case as an example, if only phase A exceeds the limit and the difference is positive, the marker is positive, and equalization bridge arm temperature control is implemented; if phases A and B both exceed the limit and both are positive, the marker can be directly positive, and equalization bridge arm temperature control is implemented; if one is positive and the other is negative, the temperature difference between phases A and B is compared, and the bridge arm with the larger temperature difference is marked, and equalization bridge arm temperature control is implemented; if phases A, B, and C all exceed the limit and all are positive, the marker can be directly positive, and equalization bridge arm temperature control is implemented; otherwise, the marker with the most frequent marker (positive if two are negative and one is positive, negative if two are positive and one is negative) is selected, and equalization bridge arm temperature control is implemented. As for the remaining bridge arms with excessively large temperature differences, this can be compensated for by temperature control of different bridge arms in the same phase.

[0034] Balanced bridge arm temperature control management strategy, such as Figure 4 As shown, For the junction temperature of the upper pipe of the bridge arm, For the junction temperature of the lower pipe of the bridge arm, For DPWM trigger junction temperature, This is the junction temperature triggered by SVPWM. If and Within a certain temperature range, SVPWM modulation is used to optimize the driver's output waveform, improving the aircraft motor's operating performance; if... Using DPWM with "000" as the zero vector, while meeting modulation requirements, it also ensures different conduction losses between the upper and lower devices' zero vectors, thereby compensating for temperature differences between the devices. When switching back to SVPWM modulation, it provides good output space for the motor; if Using DPWM with "111" as the zero vector, in At that time, switch back to SVPWM modulation. and A certain difference exists, forming a hysteresis comparison. This reduces the interference of sampling errors on the control strategy and avoids frequent modulation switching. In the actual control strategy, the number of temperature difference bridge arms and state classification are combined with the temperature control of the equalization bridge arms, based solely on... Figure 3 Select the modulation algorithm as the process marker symbol type.

[0035] To address the temperature differences between different bridge arms in the same phase, management and control strategies include... Figure 5 As shown, and For phase A, there are two bridge arms. This refers to the temperature difference of phase A bridge arm. For in-phase control of operating temperature, The return temperature is for in-phase control. and For example, if and Temperature difference When, then change The operating status of each electrical cycle is adjusted in steps according to the temperature difference. During non-operating electrical cycles, During periods of non-operation, The operating current increases, leading to The equivalent current decreases. The equivalent current increases, thus balancing , Operating temperatures of the two in-phase bridge arms; if If the temperature difference between the two bridge arms is not significant, the system returns to its initial state.

[0036] Similarly, when and Temperature difference At that time, the opposite control strategy is adopted to change The operating state of each electrical cycle; if If the temperature difference between the two bridge arms is not significant, the system returns to its initial state, which can improve the overall lifespan of the driver. Figure 8 Taking a four-way frequency divider as an example, the principle is explained. In practical applications, the number of frequency dividers can be flexibly adjusted according to the controller's computing speed and the control precision of the bridge arm thermal management to obtain better active thermal management effects.

[0037] In summary, this design for aircraft motor drives implements active thermal management from three aspects: suppressing overall temperature fluctuations of the drive, balancing the temperature of components on the same bridge arm, and balancing the temperature of different bridge arms in the same phase. This comprehensively reduces the impact of heating time and spatial unevenness on the lifespan of power devices, improves the operating temperature of the drive, and increases the utilization rate of the drive.

Claims

1. A method of active thermal management of a motor drive for an aircraft, characterized in that, A thermal network constructed using temperature-sensitive electrical parameters and a temperature sensor are comprehensively considered in relation to the measured temperature. Active thermal management control is implemented from three aspects: suppression of overall driver temperature fluctuations, temperature equalization within the same bridge arm, and temperature equalization between different bridge arms in the same phase, based on driving parameters, modulation strategies, and duty cycles. The specific active thermal management control method is as follows: (1) Overall temperature fluctuation suppression management: The aircraft will experience temperature fluctuations due to changes in heat dissipation conditions and load. The switching loss and conduction loss are considered in combination for coordinated control. The current amplitude is dynamically limited and the switching frequency is adjusted. At the same time, the temperature change rate is monitored and the current change rate is limited to slow down the temperature change. Specifically, when the aircraft increases its speed due to attitude adjustment or the heat dissipation conditions deteriorate, the overall temperature of the driver will rise in stages. At this time, the switching frequency is appropriately reduced to reduce the switching loss of the power device and the current amplitude is limited to limit the conduction loss of the power device. At the same time, the temperature change rate is monitored and the current change rate is limited by the model prediction method to reduce the driver temperature rise. Similarly, when the overall temperature of the driver drops in stages, the switching frequency and current limit are appropriately increased and the negative current change rate is limited to reduce the driver temperature drop. (2) Temperature equalization management of the same bridge arm: The temperature difference of the upper and lower power devices of the three-phase bridge arm is classified and the DPWM or DPWM or SVPWM modulation algorithm with "111" as the zero vector or "000" as the zero vector is selected according to the results. While ensuring the quality of the output waveform, the overall situation of the three-phase bridge arm is taken into account to balance the temperature and extend the overall service life of the driver. Specifically, the number and status of the bridge arm with the temperature difference of the upper and lower power devices of the three-phase bridge arm exceeding the limit are discussed and classified. The temperature difference of the upper and lower power devices of the bridge arm is evaluated according to the classification results. When the working temperatures of the upper and lower power devices are not much different, SVPWM with better modulation performance is adopted. If the temperature of the upper tube of a typical bridge arm is greater than that of the lower tube and exceeds the threshold, DPWM with "000" as the zero vector switching is adopted. Otherwise, DPWM with "111" as the zero vector switching is adopted. By managing the conduction loss when the zero vector is applied, the loss of the higher temperature power device is weakened and the loss of the lower temperature power device is compensated, so that the temperature difference is reduced and the aging process of the devices in the same bridge arm is balanced. (3) Temperature equalization management of different bridge arms in the same phase: When the temperature of the bridge arms in the same phase of different drive modules is not uniform, the working state of the device in each electrical cycle is changed according to the temperature difference, and the equivalent current value flowing through the bridge arm is adjusted to equalize the temperature of the same phase; Specifically: In order to meet the starting current requirements of the aircraft, the driver adopts a redundant design. During normal operation, the current is shunted by the bridge arms in the same phase; If the temperature of one bridge arm is greater than the temperature of other bridge arms and exceeds the threshold, the working state of its electrical cycle is adjusted according to the difference. During the operation of the aircraft, this can be equivalent to the reduction of the effective current flowing through the overheated bridge arm, the reduction of conduction loss, thereby reducing the temperature and equalizing the service life of the power devices.

2. The active thermal management method for an aircraft motor driver according to claim 1, characterized in that, The active thermal management process for the aircraft's motor drive is as follows: (a) During the self-test of the aircraft, the upper and lower power devices of different bridge arms are turned on and 1.5 times the rated current is injected for a short time. The on-state voltage drop of the device is obtained through the voltage acquisition circuit. Based on the principle that the on-state voltage drop is positively correlated with the degree of aging, the parameters of the thermal network are corrected and updated. (b) When the aircraft starts up, the motor speed is required to increase rapidly and the current carrying capacity is large. Therefore, all bridge arms are in full operation and no temperature control is performed on them. (c) After the aircraft is running stably, the torque and speed of the motor and the temperature of the controller also tend to stabilize. At this time, the driver is subjected to comprehensive active thermal management, including suppression of overall driver temperature fluctuations, equalization of temperature of the same bridge arm, and equalization of temperature of different bridge arms in the same phase. (d) When the aircraft lands, the current is gradually reduced. Temperature control is not required at this time, but the average temperature of the power devices collected by the NTC temperature sensor during the aircraft operation can be stored for updating the thermal network parameters.

3. The active thermal management method for an aircraft motor drive according to claim 1, characterized in that, When the overall temperature of the driver rises above the maximum threshold, the switching frequency is reduced to reduce the switching losses of the power devices, and the maximum current and rate of change are limited to reduce the conduction losses of the power devices. When the overall temperature of the driver drops below the minimum threshold, the switching frequency is increased to increase the switching losses of the power devices, and the minimum current and rate of change are limited to increase the conduction losses of the power devices.

4. The active thermal management method for an aircraft motor drive according to claim 1, characterized in that, The driver includes a printed circuit board, power devices, an NTC temperature sensor, conductor copper pillars, a heat sink, a relay, and a bus capacitor. The printed circuit board has a microcontroller control circuit, a signal acquisition and processing circuit, a motor drive circuit, and a power supply circuit. There are two printed circuit boards placed opposite each other. The power devices are placed on the top and bottom sides of the printed circuit boards. The bus capacitor and the relay are placed between the two printed circuit boards and arranged around the perimeter of the printed circuit boards. Conductor copper pillars are used as supports between the two printed circuit boards and electrically connect the circuits on the top and bottom printed circuit boards. The NTC temperature sensor is placed close to the power devices and between the power devices and the printed circuit boards. The heat sink is located at the top and bottom ends of the printed circuit board and is in close contact with the power devices.

5. The active thermal management method for an aircraft motor drive according to claim 4, characterized in that, Except for the heat sink, the driver is encapsulated in a stainless steel metal shell. Waterproof aviation connectors are used when the relays and bus capacitors are connected to the external circuit. The stainless steel metal shell of the driver is connected to the shielding layer of the signal cable.

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